CRLBs for Pilot-Aided Channel Estimation in OFDM System under Gaussian and Non-Gaussian Mixed Noise

The determination of Cramer-Rao lower bound (CRLB) as an optimality criterion for the problem of channel estimation in wireless communication is a very important issue. Several CRLBs on channel estimation have been derived for Gaussian noise. However, a practical channel is affected by not only Gaussian background noise but also non-Gaussian noise such as impulsive interference. This paper derives the deterministic and stochastic CRLBs for Gaussian and non-Gaussian mixed noise. Due to the use of the non-parametric kernel method to build the PDF of non-Gaussian noise, the proposed CRLBs are suitable for practical channel environments with various noise distributions

Satellite estimates of wide-range suspended sediment concentrations in Changjiang (Yangtze) estuary using MERIS data

The Changjiang (Yangtze) estuarine and coastal waters are characterized by suspended sediments over a wide range of concentrations from 20 to 2,500 mg l-1. Suspended sediment plays important roles in the estuarine and coastal system and environment. Previous algorithms for satellite estimates of suspended sediment concentration (SSC) showed a great limitation in that only low to moderate concentrations (up to 50 mg l-1) could be reliably estimated. In this study, we developed a semi-empirical radiative transfer (SERT) model with physically based empirical coefficients to estimate SSC from MERIS data over turbid waters with a much wider range of SSC. The model was based on the Kubelka–Munk two-stream approximation of radiative transfer theory and calibrated using datasets from in situ measurements and outdoor controlled tank experiments. The results show that the sensitivity and saturation level of remote-sensing reflectance to SSC are dependent on wavelengths and SSC levels. Therefore, the SERT model, coupled with a multi-conditional algorithm scheme adapted to satellite retrieval of wide-range SSC, was proposed. Results suggest that this method is more effective and accurate in the estimation of SSC over turbid water

Interaction between graphene and SiO2 surface

With first-principles DFT calculations, the interaction between graphene and SiO2 surface has been analyzed by constructing the different configurations based on {\alpha}-quartz and cristobalite structures. The single layer graphene can stay stably on SiO2 surface is explained based on the general consideration of configuration structures of SiO2 surface. It is also found that the oxygen defect in SiO2 surface can shift the Fermi level of graphene down which opens out the mechanism of hole-doping effect of graphene absorbed on SiO2 surface observed in experiments.Comment: 17 pages, 7 figure

Comparison of lipase-catalyzed synthesis of cyclopentadecanolide under organic and biphasic systems

Methyl 15-hydroxy-pentadecanate, which is made from Malana oleifera chum oil, is an ideal material to synthesize cyclopentadecanolide, an important macrocycle musk, with wide applications in the fields of perfume, cosmetic, food and medicine, etc. One kind of screened lipase from Candida sp.GXU08 strain was used to catalyze the synthesis of cyclopentadecanolide from methyl 15-hydroxy-pentadecanate. Traditionally, the catalytic reaction went on under organic solvent system, while an ultrasonic technology was innovatively used in water/organic solvent biphasic system to systhesize cyclopentadecanolide and received good catalytic effect. Both organic and biphasic systems had the same optimal conditions as: substrate concentration= 8 mmol/l, T= 40°C, ω = 180 r/min, pH= 6.0 to 6.5, ultrasonic time of 30 min, output power of 200 W and using lipase solution/lipase power and reaction system twice greatly increased the production of cyclopentadecanolide. It showed that, the maximum production of cyclopentadecanolide was 47.77×10-3mg/U in biphasic system under the optimal conditions, which was 3.285 times of that in the organic system. It was also found that the production of cyclopentadecanolide in biphasic system was always higher than that in the organic system, which saved the process of freeze drying and improved the production of cyclopentadecanolide. It was verified that methyl 15-hydroxy-pentadecanate was directly cyclized into cyclopentadecanolide in the organic system while in the biphasic system, methyl 15-hydroxy-pentadecanate was hydrolysed into 15-hydroxypentadecanoic acid firstly and then cyclized into cyclopentadecanolide.Key words: Lipase, cyclopentadecanolide, Malana oleifera chum, biphasic system, ultrasonic